Telephone system



3 sheets-Sheet Filed July 1932 INVENTOR W C. OAKES ATTORNEY Jan. 9;1934. w. c. oAKEs 1,942,487

TELEPHONE SYSTEM Filed July 1, 1932 5 Sheets-Sheet 2 poumzsl L lNl/ENTORW C. OAKELS A TTORNEY Jan. 9, 1934- w. c. OAKES TELEPHONE SYSTEM FiledJuly 1, 1932 3 Sheets-Sheet I5- m at lNl/EN TOR W 6. 0A K E 5 BY A 7'Tom/Er Patented Jan. 9, 1934 UNITED STATES ATEN OFFICE 1,942,487TELEPHONE srsirEM William C. Oakes, Arlington, N. J;,'assignor to BellTelephone Laboratories, Incorporated, 7 New York, N. Y a corp'or'ationof New York Application July 1, 1932. Serial No. 20,413 8 Claims. (Cl.179-43) This invention relates to telephone systems and particularly tointerofiice trunks for such systems.

An object of this invention is to improve the facilities forestablishing telephone connections over trunks between ofiices.

Heretofore trunks have been provided in which calls incoming over atrunk to an Office may be transferred from one called subscriber toanother. A feature of the present invention is theprovision in a two-wayoffice trunk of a so-called joint trunk operation arrangement. Theincoming end of this trunk is provided with two branches, oneterminating at a local board which may be termed a local trunk, and theother at a toll board which may be termed a toll trunk. Means isprovided for transferring incoming calls answered at one of these boardsto the other board. This arrangement may be such that incoming callswill be answered normally at the local board and then ifv it is foundthat a tollconnection, that may be extended from the toll board, is.desired the local operator calls up the toll operator and asks her tovconnect with the tolltrunk at her board. When the toll operator has madethis connection the local operator disconnects from the local trunk andthe transfer of the call is thereby completed to the ,toll trunk.

Another feature of this invention is an arrangement whereby busy signalsare provided at the two boards to indicate trunk busy conditions. .When.the call is first answered by the local operator the busy condition isestablished at the toll operators position for the toll trunk and whenthe toll operator answers the call a busy condition is established atthe local operators position for the local trunk.

Another feature is an arrangement whereby if the call is answered by thelocal operator the toll operator cannot interfere with this connectionand likewise after the connection has been transferred to the tollopeartor the local operator cannot interfere with the connection, shouldthe busy condition be disregarded and, an attempt be made to break in onan established connection.

Referring now to the. drawings, Figs. 1, 2 and 3 may be connected asshown in Fig. 4 and the invention is illustrated in these figures withthe principal parts of a local trunk terminating at the localswitchboard shown in Fig. 1, and the principal parts of a toll trunkterminating in a toll board shown in Fig. 3, while in Fig. 2 theremaining circuit arrangements of these two trunks are shown terminatingin a trunk incoming from an automatic office.

As this invention is concerned primarily with calls incoming over atrunk from an automatic office, descriptions will be made of such a;call incoming over the trunk: 200 from an automatic ofiice to the localtrunk terminating in jacks 1'00 69 and 101 to be answered by a localoperator and howthrough jack 100 this call answered at the localoperators position may be transferred to the toll trunk to beanswered bythe toll opera: tor through jack 3,00.

Referring now to the drawings when the trunk 200 incoming from theautomatic office is seized at this oflice the battery and ground,normally connected to the tip and ring conductors and causing relay 202to be in operated condition, are 79 reversed to causev the operation ofthe polarized relay 201 and the release of relay 202 while relay 104remains operated. The circuit for these relays may be traced frombattery over the ring conductor, lower inner armature and back contactof relay 203, contact of relay 102, lower righthand winding of repeatingcoil 103, Winding of relay 104, windings of relays 202 and 201 inseries, upper right-hand winding of repeating coil 103, contacts ofrelay 102, inner upper armature and so back contact of relay 203 to the.ring conductors back to the ground at the distant automatic ofiice.Relay 201 inoperating connects ground to the circuit for lamp 106 tocause this lamp .to light .to indicate to the local operator that a call35 is incoming over trunk 200. The release of relay 202 causes theoperation of relay 204 over acircuit from battery, winding of thisrelay, armature and back contact of relay 202 to ground at contacts ofrelay 203. Relay 204 in operating closes a circuit for the operation ofrelay 1.09 from battery through the winding of this relay, contacts ofrelays 110 and 111, left-hand armature and front contact .of relay 204to ground. Relay 204 also closesa circuit for the operation of a busysig- .,1 mil 113 from battery, right-hand armature and front contact ofrelay 204,v winding of the busy signal 113 to ground. This signal isassociated with the jack 101 which is used for outgoing calls over thelocal trunk and serves to warn that the local trunk is busy. Relay 109in operating closes a holding circuit for itself through its innerrighthand armature and front contact to ground at relay 204. Relay 109in operating also connects at its middle right-hand armature and frontcontact a ground for the lead 117. This ground extends to the sleeveterminal of the-toll trunk jack 300 to make this trunk busy. The circuitmay be traced from the ground at relay 109, lead 117, winding of relay305 to battery. Relay 305 1 2 0 operates and in turn closes an obviouscircuit for the operation of relay 313. This latter relay makes thesleeve terminal of jack 300 busy by connecting battery thereto at itsarmature and front contact and also lights the trunk signal 314. Theoperation of relay 109 also connects battery at its inner left-handarmature and front contact, resistance 135, winding of relay 115 to lead118 which causes the jack 101 to test busy on its sleeve. This batteryconnection is also extended to the sleeve of the connection from thislocal trunk to outgoing toll connections that may be established throughthe tip and ring conductors and sleeve at 120. This is to prevent callsincoming at this point 120 through this local trunk from outgoing overthe trunk 200 to the distant automatic ofiice. Relay 109 also at itsmiddle left-hand armature and back contact opens a connection for thering conductor through the leads at 122 that may extend to multipleoutgoing trunk jacks at other toll positions which, as far as thisinvention is concerned, is of no importance. It also opens at its outerleft-hand armature and back contact the tip connection of the trunkoutgoing to the toll oflice at 120.

When the local operator inserts plug 107 into jack 100 to answer thiscall relay 123 is operated over a circuit from battery, sleeve terminalsof plug 107 and jack 100, winding of relay 123 to ground. Relay 123 inoperating closes a circuit for relay 210 from battery, winding of relay210, lead 133 to ground at relay 123. Relay 210 in operating preventsthe call from being transferred at this time should the toll operatorinsert the plug 303 into jack 300, and to make the transfer depend onthe local operator first removing the plug 107 from jack 100 as willhereinafter be described. After plug 107 has been fully seated in thejack 100, a circuit is closed through the cord circuit associated withthe plug for relay 125 from battery, the tip terminals of plug 107 andjack 100, upper left-hand winding of repeating coil 103, windings ofrelay 125, lower lefthand winding of repeating coil 103 over the ringterminals of jack 100 and plug 107 to ground. This causes the operationof relay 125 which in turn closes an obvious circuit for the operationof relay 127. Relay 127 closes a holding circuit for itself from batterythrough the winding of this relay, inner right-hand armature and frontcontact to ground at the armature and front contact of relay 123. Relay127 in operating short-circuits relays 201 and 202 at the outer lefthandarmature and front contact. Relay 201 releases and opens the circuit forthe call signal 106. The condenser 130 is also connected by relay 127across the right-hand windings of repeating coil 103 for talkingpurposes. Relay 127 also connects battery at its inner left-handarmature and front contact for the operation of relay 110 over a circuitto ground at relay 204. Relay 110 now looks under control of relay 204independent of relay 127.

If the incoming call from the automatic ofiice that has been answered bythe local operator is to be completed by a toll operator through thetoll trunk shown in Fig. 3 the local operator will, as stated,communicate with the toll operator in the usual manner by means of anorder wire or recording trunk commonly used in automatic exchanges fortransmitting instructions between operators. The toll operator will beinstructed to handle the call and she in turn will insert the answeringplug 303 of a toll cord into the jack 300 of this toll trunk and thelocal operator may remove plug 107 from jack 100 whereupon the transferwill take place. insertion of plug 303 into jack 300 is the operation ofrelay 304 from ground through the upper winding of this relay, thesleeve terminals of jack 300 and plug 303 to battery on the sleeve ofthe toll cord. Relay 304 in operating closes an obvious circuit for theoperation of relay 306. Relay 306 closes obvious circuits for theoperation of relays 307 and 308. Relay 307 closes an obvious circuit forrelay 211. The operation of relay 211 provides a ground at its lowerarmature and front contact for subsequent operation of relay 203 andother circuits, the purpose of which will become apparent hereinafter.Relay 306 short-circuits the winding of relay 311 and the upper windingof relay 312.

If now the local operator removes plug 107 from jack 100 relays 125 and123 will release and these relays in turn release relay 127. Relay 123The first effect of the by removing ground from the conductor 133releases relay 210. Relay 210 in releasing completes a circuit for theoperation of relay 203 from battery, winding of this relay, upperarmature and back contact of relay 210, lower armature and front contactof relay 211 to ground. Relay 210 also provides at this time asubstitute busy battery potential on'lead 118 from battery, lowerarmature and back contact of this relay, upper inner armature and frontcontact of relay 211, re sistance 135, relay 115 to lead 118. Relay 203in operating locks through its outer lower armature and front contact tothe ground at contacts of relay 211 independent of relay 210, so thatincase the local operator should attempt to override the busy conditionshe cannot cut off the toll trunk from the toll operator by causing theoperation of relay 210 and release relay 203. Relay 203 in operatingtransfers the tip and ring conductors of the trunk 200 to the tip andring conductors of the toll trunk from the tip and ring conductors ofthe local trunk. It also removes the ground from the lead holding relay204 operated. Relay 204 is now released and thereby causes the releaseof relays 109 and 110 and opens the circuit for the busy signal 113.Relay 109 in releasing causes ground to be removed from conductor 117.Relay 203 in operating also applies ground at its make-beforebreakcontacts to the lead 212 and as relay 311 is short-circ'uited by relay306 a circuit is now completed for maintaining relay 305 operated. Itwill be seen now that the toll trunk is completely connected through therepeating coil 316 to the distant ofilce, the connection to the tip andring conductors from the distant office over trunk 200 extending throughcontacts of relay 306, condenser 317 and the left-hand windings ofrepeating coil 316, while the right-hand side of the repeating coil isconnected through the tip and ring conductors to the toll operatorthrough the condenser 318 and contacts of relay 308. The toll operatormay now receive the desired information from the distant automaticoffice and extend the connection to the desired party in the usualmanner.

If the local operator disconnects before the toll operator has taken upthe toll trunk, the line lamp 106 will relight at the local operatorsboard showing her that this is the case. When the call is taken up bythe toll operator th lamp 106 will be extinguished.

When the toll operator at the close of the conversation withdraws herplug 303 from jack 300, the circuit will return to normal by the releaseof relays 304, 306, 307, 308, 211, 203, 305 and 313.

What is claimed is:

1. In a telephone system, a two-way trunk, a local trunk, a toll trunk,said last mentioned two trunks being associated with one end ofsaidtwoway trunk, means for normally answering calls incoming to saidend of the two-way trunk over the local trunk, means for answeringincoming calls over the toll trunk, and means for transferring incomingcalls answered over the local trunk for answering over the toll trunkoperative on the seizure of the toll trunk and release of the localtrunk.

2. In a telephone system, a two-way trunk, a local trunk, a toll trunk,said last mentioned two trunks being associated with one end of saidtwo-way trunk with the local trunk normally connected to the two-waytrunk and the toll trunk normally disconnected from said two-way trunk,and means for disconnecting the local trunk and connecting the tolltrunk to the twoway trunk, responsive to the seizure of the local trunkfollowed by the seizure of the toll trunk and then by the release of thelocal trunk.

3. In a telephone system, a two-way trunk, a local trunk, a toll trunk,said last mentioned two trunks being associated with one end of saidtwo-way trunk, means for answering calls incoming to said end of thetwo-way trunk over the local trunk, means for answering incoming callsover the toll trunk, means for transferring incoming calls answered overthe local trunk for answering over the toll trunk operative on theseizure of the toll trunk and release of the local trunk, means fornormally preventing the incoming call from being answered over the tolltrunk after it has been answered over the local trunk, and means forpreventing the incoming call from being again answered over the localtrunk after the call has been transferred to and answered over the tolltrunk.

4. In a telephone system, a two-way trunk, a local trunk having ananswering terminal and a calling terminal, a toll trunk having ananswering terminal, said last two trunks being associated with one endof said two-way trunk, means responsive to a call incoming over thetwo-way trunk for establishing a busy condition at the calling terminalof the local trunk and at the answering terminal of the toll trunk,means responsive to the answering of the call over the answeringterminal of the local trunk for preventing the answering of the callover the answering terminal of the toll trunk.

5. In a telephone system, a two-way trunk, a local trunk having ananswering terminal and a calling terminal, a signal at the answeringterminal, a signal at the calling terminal, a sleeve conductor at theanswering terminal, a sleeve conductor at the calling terminal, a tolltrunk having an answering terminal, a sleeve conductor at the answeringterminal of said toll trunk, said last mentioned two trunks beingassociated with one end of said two-way trunk, means responsive to callsincoming over the two-way trunk for actuating the signal at theanswering terminal of said local trunk and for establishing a busycondition on the sleeve conductor at the calling terminal of said localtrunk and on the sleeve conductor at the answering terminal of the tolltrunk and for actuating the busy signal at the calling terminal of saidlocal trunk, and means responsive to the answering of the call over thelocal trunk answering terminal for preventing answering of the call overthe answering terminal of the toll trunk.

6. In a telephone system, a two-way trunk, a local trunk having ananswering terminal and a calling terminal, a signal at the answeringterminal, a busy signal at the calling terminal, a sleeve conductor atthe answering terminal, a sleeve conductor at the calling terminal, atoll trunk having an answering terminal, a sleeve conductor at theanswering terminal of said toll trunk, said last mentioned two trunksbeing associated with one end of said two-way trunk, means responsive tocalls incoming over the twoway trunk for actuating the signal at theanswering terminal of said local trunk and for actuating the busy signalat the calling terminal of said local trunk and for establishing a busypotential on the sleeve conductor at the answering terminal of the tolltrunk, means for transferring an incoming call from the answeringterminal of the local trunk to the answering terminal of the toll trunkresponsive to the seizure of the answering terminal of the local trunkin answering the call followed by the seizure of the answering terminalof the toll trunk and by the release of the answering terminal of thelocal trunk, and means responsive to said transfer for establishing abusy potential on the sleeve conductor of the calling terminal of thelocal trunk.

'7. In a telephone system, a two-way trunk, a local trunk having ananswering terminal and a calling terminal, a sleeve conductor at saidcalling terminal, a busy signal at said calling terminal, a call signalat said answering terminal, a toll trunk having an answering terminal, asleeve conductor at said answering terminal of the toll trunk, a busysignal at said answering terminal of the toll trunk, means responsive toa call incoming over the two-way trunk for actuating said call signaland said busy signal and for establishing a busy potential on saidsleeve conductors, and means responsive to the answering of the callover the answering terminal of the local trunk for disabling the callsignal and for preventing the answering of the call over the answeringterminal of the toll trunk.

8. In a telephone system, a two-way trunk, a local trunk having ananswering terminal and a calling terminal, a sleeve conductor at saidanswering terminal, a call signal at said answering terminal, a sleeveconductor at said calling terminal, a busy signal at said callingterminal, a toll trunk having an answering terminal, a sleeve conductorat said answering terminal of the toll trunk, a busy signal at saidanswering terminal of the toll trunk, means responsive to a callincoming over the two-way trunk for actuating said call signal and saidbusy signal and for establishing a busy potential on the sleeveconductor at the calling terminal of the local trunk and on the sleeveconductor at the answering terminal of said toll trunk, means responsiveto the answering of the call over the answering terminal of the localtrunk for disabling said call signal, means for thereafter transferringthe incoming call from said answering terminal of the local trunk to theanswering terminal of the toll trunk responsive to the seizure of theanswering terminal of the toll trunk followed by the release of theanswering terminal of the local trunk, and means responsive to saidtransfer for establishing a busy potential on the sleeve conductor ofthe answering terminal of said local trunk.

WILLIAM C. OAKES.

